As we know, the sunglasses are usually worn for the protection for the eyes from the uv and other bad lights. However, the sunglasses nowadays are more and more regarded as the accessories to add the beauty and coolness. The persons wearing the sunglasses at parties are just for the cool appearance. They will look so fashionable at wearing the sunglasses which will be suitable with their clothing.
Well, it seems that you have not attended a lot of parties. So, in my personal opinion, the reason why people choose to wear a pair of sunglasses over parties, is to make them appear much more attractive and mysterious to other people, also, they would not like to be recognized in an easy way. In the meantime, some sunglasses are really cool you know, such as Armani sunglasses and Polo sunglasses.
Well, actually there are many people who wear sunglasses when they are in the parties. And you should know that there are too reasons for them to wear. First, they just want to make them look attractive, cool, and beautiful for there are many types of sunglasses which have beautiful design and perfect frames. By wearing them when they are in the party, it can make them look more gorgeous. Also, in my opinion, it is probably because they want to protect themselves from colourful light. As we know that sunglasses are designed with special use. That is to darken the light and protect people's eyes. In this way, they can be helpful to protect the eyes. But on the other hand, it is bad to wear sunglasses all the time. In this way, it will just make your eyes be accustomed to the dark light. So when you take off your sunglasses, you will feel uncomfortable and your eyes will be hurt by the bright light. In serious situation, it will lead to many eye diseases. So just be careful about it.